It is known to multiplex several uplink transport channels onto a dedicated physical channel for transmission in order to enable an effective use of available resources.
The technical specification 3GPP TS 25.211 V3.7.0: “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical channels and mapping of transport channels onto physical channels (FDD) (Release 1999)” describes for example a multiplexing of Layer 1 transport channels onto physicals channels in the FDD (frequency division duplex) mode of the universal mobile telecommunications system (UMTS) terrestrial radio access (UTRA).
According to this specification, a transport channel (TrCH) is defined by how and with what characteristics data is transferred over the air interface. Dedicated transport channels are referred to by dedicated channel (DCH). Physical channels are furthermore defined by a specific carrier frequency, a channelization code and, on the uplink, a relative phase.
During an Radio Resource Control (RRC) connection several TrCHs may be multiplexed in the uplink by a terminal onto one code composite transport channel (CCTrCH), which is subsequently mapped to the data part of a dedicated physical channel (DPCH). This is illustrated by FIG. 1, which corresponds to a figure in the Technical Specification 3GPP TS 25.212 V3.4.0: “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Multiplexing and channel coding (FDD) (Release 1999)”.
As shown in FIG. 1, data provided by the MAC (Medium Access Control) and higher layers arrives at the coding/multiplexing unit 11 in form of a transport block sets on a transport channel TrCH#1 once every transmission time interval (TTI). The TTI is transport channel specific and can take one of the values 10 ms, 20 ms, 40 ms and 80 ms. First, different processing steps are applied to the transport block sets of each transport channel TrCH#1 separately, beginning with adding cyclic redundancy check (CRC) bits to each block 12 and terminating with rate matching 13. The processing steps applied to different transport channels are indicated in FIG. 1 by rectangles 14 grouping these steps. Afterwards, different TrCHs are multiplexed to a single CCTrCH 15. The CCTrCH is mapped after further processing onto a physical channel PhCH#1 16. The physical channel then undergoes spreading, scrambling and modulation. In case of multicode, the same applies to the other physical channels, denoted PhCH#2 etc. in the figure. For the details of the processing steps, which are depicted in FIG. 1 for one transport channel TrCH#1 and for the CCTrCH, it is referred to the cited specification TS 25.212.
The DPCH onto which the CCTrCHs is mapped consists of a dedicated physical control channel (DPCCH) and one or more dedicated physical data channels (DPDCH). The DPDCHs comprise the user data of the TrCHs. For the different DPDCHs different spreading codes are used, which enables a simultaneous WCDMA (Wideband Code Division Multiple Access) transmission. The DPCCH comprises predefined pilot bits to support channel estimation for coherent detection, transmit power control (TPC) commands and a transport format combination indicator (TFCI). DPCCH and DPDCHs are I/Q multiplexed within each radio frame with complex scrambling.
In the uplink, the multi-code operation is possible, if the bit rate of the CCTrCH exceeds the maximum bit-rate of the uplink DPDCH and the maximum allowed amount of puncturing has already been applied. In this case, a spreading factor (SF) equal to 4 has then to be used for the different codes and up to 6 parallel DPDCHs can be used, while only one DPCCH per connection is possible.
When the connection is set up, the terminal is given the minimum allowed SF of the uplink channelisation code for the data part and the variable rate is handled in a dynamic rate matching by changing the DPDCH bit rate (SF) frame by frame or by repeating or puncturing the code bits to achieve the total physical channel bit rate. In the uplink direction repetition is preferred. Puncturing is used to avoid multicode transmission or when facing the limitations of the User equipment transmitter or Node B receiver.
The relative power level is set such that for higher bit rates the power of the DPCCH is higher, thus enabling a more accurate channel estimation, and the overhead, i.e. DPDCH vs. DPCCH power, of the DPCCH is still lower.
Since several TrCHs may be multiplexed onto one CCTrCH, and since the quality, and in particular the Eb/No (bit energy per noise interference) requirements can be different in each transport channel, a rate-matching attribute is introduced for each TrCH, which is used in balancing the Eb/No values of the radio connection for a static or service specific rate matching.
According to the specification TS 25.212, higher layers assign a rate-matching attribute for each transport channel. The rate-matching attribute is used to calculate a rate matching value when multiplexing several TrCHs for the same frame. The attribute is semi-static and can only be changed through higher layer signaling. By adjusting the rate-matching attribute, an admission control (AC) is thus able to fine-tune the quality of different bearer services in order to reach an equal or near equal symbol power level requirement. Success of the static rate matching depends on, e.g., how correct the Eb/No value is in respect to the quality—e.g. BLER—target.
With the aid of the rate matching attribute and the TFCI of the DPCCH, the receiver can calculate backwards the rate matching parameters used and perform the inverse operation.
Static and dynamic rate matchings 13 are done simultaneously, they are also indicated in FIG. 1.
Neither the Eb/No nor the quality of any TrCH set up during the same RRC connection is available from the conventional implementations.
In order to overcome the effect of the possible incomplete static rate matching in the measured quantities, it would be an advantage, if uplink connection based measurements could be carried out for each bearer service or TrCH multiplexed onto one CCTrCH.
Eb/No is also in general a key figure for receiver performance and can be employed for a variety of functions, as well in controlling as in evaluation. Moreover, other parameters associated to specific TrCHs, in particular quality parameters like BER (Bit Error Rate) and/or BLER (Block Error Rate), can be of interest, which parameters are only available for entire DPCHs in the current implementations.